ALONE IN THE UNIVERSE

Why Our Planet Is Unique

The British astrophysicist and prolific science writer presents a skillful, contrarian examination of the possibility of intelligent life beyond Earth.

Gribbin (In Search of the Multiverse, 2010, etc.) begins with a lucid discussion of galaxy, star and planet formation. Since life on Earth appeared instantly (in geological terms) after the young planet settled down, it’s mathematically probable that life develops quickly on habitable planets, and planets themselves seem almost universal. Sadly, Gribbin concludes that conditions favorable to habitable planets are rare. Liquid water must be present. If the Earth’s orbit (amazingly circular, another rarity) were one percent further or five percent nearer to the sun, the inhabitants of Earth would be out of luck. Another blessing is our huge moon, which stabilizes the Earth; it and the huge planet Jupiter sweep the solar system largely clear of debris that would normally bombard our planet. Our sun is extraordinarily well behaved and long lived. Larger stars burn out too quickly to allow time for life, and most smaller ones are too unstable. Finally, earthly life’s four-billion-year progression to Homo sapiens included regular disasters (asteroid strikes, abrupt climatic changes, freezeovers), which are guaranteed to continue and which make the survival of advanced civilization (as opposed to simple life) problematic.

Within most readers’ lifetimes, astronomers will possess technology to detect water, oxygen and tolerable temperatures around extra-solar planets. Predictions of scientific discoveries have a poor success rate, so readers should keep their hopes up as they enjoy this thought-provoking history of the universe and the prerequisites of life.